Tying material and method of coating same



Sept. 13, 1960 H. P. YOUNG ETAL TYING MATERIAL AND METHOD OF COATING SAME Filed July 22, 1954 .15 wan/imam United States Patent TYING MATERIAL AND lVIETHOD OF COATING SAME Hobart P. Young, Winnetka, 111., and John J. Hickerson, Albuquerque, Mex., assignors, by direct and mesne assignments, to Signode Steel Strapping Company, Chicago, 111., a corporation of Delaware Filed July 22, 1954, Ser. No. 444,992 39 Claims. (Cl. 117-49) The present invention relates to coated metallic strands or ligatures employed for packaging, such as metal wire or strapping, and to methods of preparing the same.

Thin metallic bands or strapping are employed in the packaging of materials to secure the packages. In one use, such b ands or strapping are placed around the package to be secured and, by the use of suitable tools, drawn tight and the overlapping ends secured together by crimping or other suitable means. The strapping may also be used to secure heavy objects in place, as, for example, in freight cars. In accordance with the present invention, such bands or strapping are provided with a protective coating which improves their appearance and protects them against abrasion and corrosion. While baked enamels have hitherto been employed in some cases as coatings for such strapping, such coating materials are unduly expensive, and by reason of the nature of the coating and baking operations involved, the speed of coating is much slower than that of manufacture of the strapping. Hence its use either greatly slows down the rate of production of finishing the strapping if the coating process is incorporated in the production line, or requires a separate finishing operation. A similar situation applies when wire is employed in packaging.

In accordance with the present invention, the strapping or other tying material, hereinafter generally referred.

to as the strand, is provided with a plastic coating under conditions which permit the coating operation to be conducted as a part of the production and finishing operations in the manufacture of the strapping and Without reduction of the speed of movement of the strapping in the production line. The coating must fulfill certain exacting requirements. It must be capable of application at high rates of speed and, in accordance with this invention the coating. material is a moderately high melting material and is applied in molten form, so that it can be rapidly cooled in the continuing movement of the strapping in connection with the manufacturing operation. It is also necessary that the coating provide adequate corrosion protection even when applied in very thin films and that it provide a hard and abrasion resistant film. The coating must be flexible and adherent, to withstand bending, as at the corners of packages to which the strapping is applied. When used for tying packages, it is also important that the coating have a property known as slip, so that the coated strapping will slide over the surfaces of the packages to which the strapping is applied and so that overlapping surfaces of the strapping, evenwhen held together under pressures such as are employed in tensioning the strapping on a package, can slide over each other Without excessive tension and at the same time have sufiicient friction so that they are held together by the crimping or fastening operation. With bare or oxidecoated strapping and with baked enamel coatings, it has heretofore been necessary to apply a wax or waxlike film to secure the desired slip.

In accordance with the present invention, coated strands which meet the requirements set forth above may be readily and rapidly produced while the strands are in rapid movement in a production line, suitable coating material being employed under conditions which permit the rapid movement of the strand. The invention will be fully understood from the following description, illustrated by the accompanying drawing, in which suitable equipment for carrying out the coating operation is diagrammatically shown.

Referring to the drawing, the numeral 10 designates the strand, for example, strapping which is produced by conventional preliminary operations, not shown, in which thin, cold rolled steel sheet is slit to form bands of a suitable width and the bands deburred on the edges. The strapping, entering the finishing operations as illustrated in the drawing, is thus an edge-finished thin metal band of a width and thickness suitable for use in packaging. For example, the band may be 0.020 inch thick and inch wide, although other widths and thicknesses are used, depending upon the use to which the band is to be placed. Although only one band is shown in the di agrammatic illustration in the drawing, it will be understood that a considerable number of such bands, as produced in the slitting and edge-finishing operation, may be processed simultaneously.

The strapping entering the processing operation is first subjected to a cleaning operation. Thus, it may be guided over a suitable roller 11 and passed through a molten lead bath 12 maintained at a temperature of say 750 to 950 F. In this bath a cleaning action takes place, surface adherent material being removed, and in the case of oil or other organic matter, burned away. The temperature of this bath is not critical, and is suflicient to effect cleaning and if desired, to heat the strapping to a temperature at which bluing may be effected as hereinafter set forth. A suitable bath may be 8 to 10 feet long. The strapping is guided through the bath by guide rollers 13 and 14 or by other suitable means, and emerges through a vertical chute 15 having a funnel shape top 16, which is filled with charcoal. The slow combustion of the charcoal maintains in this chute an atmosphere of carbon monoxide and carbon dioxide and the charcoal also serves to effectively wipe the molten lead from the strapping. The strapping may be at a temperature of 750 to 800 F. as it emerges from the charcoal. Other cleaning methods may be employed. For example the strapping may be passed through a heated conduit, pref erably in a non-oxidizing atmosphere, in which adherent oil or organic matter is burned oif.

After cleaning the strapping may be immediately cooled to a temperature suitable for the coating operation as hereinafter described. If desired, the strapping may be subjected to a bluing operation after leaving the lead bath or other cleaning device, in which case the cleaning device is maintained at a somewhat higher temperature of, say, 850 to 950 F. In such case the strapping after emerging from the cleaning operation has a temperature of at least 800 F. and may be subjected to a longer exposure to air to effect bluing, in the customary manner.

In the procedure illustrated in the drawing, the strapping, after leaving the charcoal chute, passes vertically through a duct 17 in which the surface of the strap becomes blued and is at the same time somewhat cooled. The strap after emerging from the lead bath, and after bluing if desired, passes over guide roll 18 and through guide rolls 19, from which it passes into the container or tank 20, in which it is immersed in the molten coating material employed in accordance with the present invention. In the tank 20 it is forced to pass below the surface of the molten coating material by the action of guide roll 21. The tank 20 is provided with a heating jacket or other suitable heating means and is maintained at a temperature suitable for keeping the coating composition in mol ten condition and for effecting the coating of the straping. The composition may suitably be maintained at a temperature of 350 to 560 F. and the strapping enters the bath preferably at a somewhat higher temperature, say 500 to 700 F. although it may enter the bath at a temperature approximately the same as the temperature of the molten coating composition. In general, it is preferred that the temperature of the strapping as it enters the coating tank be from about 50 to about 200 F. above that of the coating composition.

The strapping leaves the tank through wipers 23, which may suitably be tungsten carbide rods or plates, although other suitable wiping devices such as glass fiber wicks or the like may be employed. The wipers are set to secure the desired thickness of coating on the strapping, suitable thicknesses of coating being, for example, in the range of 0.00005 to 0.00020 inch, although thicker coatings, say up to 0.001 inch may be applied if a greater degree of climatic or corrosion resistance is desired. The thickness of the coating is likewise influenced by the speed and temperature of the strapping and the temperature of the bath.

After leaving the coating tank 20, the strapping is at once guided by suitable guide rolls 24, 25 and 26 through a cooling or quenching tank 27 containing Water, suitably at a temperature of 50 to 150 F. or at least below 200 F. The strapping then passes on to conventional reeling machinery, not shown.

In the event that the strapping is not to be blued, the temperature of the lead bath is kept in the lower portion of the range hereinbefore set forth, so that the strapping emerges from the bath at a temperature not over 800 F., and the path through which the strapping travels before entering the coating bath is made as short as possible so as to reduce the contact of the hot strapping with the air to a minimum.

The strapping, in either case, whether blued or not, while hot, enters the coating bath which is maintained at a temperature in the order of 350 to 560 F. In the bath, the principal constituent of the coating composition is a nylon or polymeric amide (sometimes designated superpolyamide) derived from a polyalkylene diamine and an aliphatic dicarboxylic acid. It is preferred that the nylon employed be a polymer of the amide resulting from the reaction of hexamethylene diamine with adipic acid, the extent of polymerization being indicated by a melting point (in air) in the range from 160 to 250 C. (320 to 480 F.). Such nylons may be designated as 6-6 nylons, since both the diamine and the dicarboxylic acid employed in forming the monomeric salt have six carbon atoms. The number of carbon atoms in the diamine employed in forming the monomer of the nylon employed may be from 4 to 8 and the number of carbon atoms in the dicarboxylic acid may be from to 10. Thus the nylons employed suitably may be polymers of the monomer derived from the reaction of hexamethylene diamine and sebacic acid; of hexamethylene diamine and suberic acid; of pentamethylene diamine and adipic acid; of pentamethylene diamine and suberic acid; of octamethylene diamine and adipic acid or of octamethylene diamine and sebacic acid. The polymers employed are those having melting points in the range hereinbefore stated.

In preparing the coating material to be employed in accordance with the present invention, there is incorporated in the nylon a softening agent of the class consisting of the abietic acid derivatives, long chain aliphatic amines having 12 to 16 carbon atoms and alkyl aryl sulfonamides. Suitable abietic acid derivatives are rosin.

and residual high melting point rosin known as Vinsol, the methyl esters of abietic acid and dihydroabietic acid, the glycerol esters of rosin and of hydrogenated rosin and dihydroabietylarnine and its salts with lower fatty acids, as the acetate, and mixtures thereof. The proportions of the softening material incorporated in the nylon mixture may be from 1 to 50% and preferably from 10 to 33%. In general it is preferred that residual high melting point rosin, known commercially as Vinsol and having a softening point by the A.S.T.M. ring and ball method of about 220 to 230 F., be incorporated in the nylon in proportions of from 10 to 33% of the mixture and preferably about 20%. The glycerol esters of rosin (ester. gum) and of hydrogenated rosin are preferably employed in similar proportions.

The nylon mixtures employed in carrying out the present invention have a lower melting point and are less viscous when molten than the nylon constituent and are distinguished by the fact that they are capable of forming a thinner and more adherent protective coating than the nylon constituent alone. The coatings formed by these mixtures are hard, smooth and substantially transparent and do not impart an objectionable color to the strapping. They are sufficiently flexible, resistant to abrasion, and prevent corrosion of the strapping. Furthermore, such coatings, in general, without waxing, have the desired slip in use and when superimposed portions of the strapping are held together under substantial pressure.

In order to measure the slip in a manner simulating and in some degree indicating the pull required to slide one piece of strapping over another under the conditionsv existing in tools ordinarily employed for tightening and securing the strapping around packages, the following method may be employed.

Two pieces of strapping of a size suitable for use in. packaging, for example, /4 inch wide and 0.020 inch thick are superimposed over a stainless steel bar 7 inch wide. A weight of 45 pounds is then applied to the superimposed straps over the bar, this giving a pressure of approximately pounds per square inch over a contact area of sq. in. The upper strap is clamped firmly in place and tension is applied to the lower strap through a spring scale until the lower strap is caused to slip. The tension shown by the scale is an inverse indication of slip, the slip being greater the lower the tension indicated. Under these conditions, a waxed, blued steel strapping shows. a slip in the order of 11 to 13 pounds. In comparative tests, the results secured in this way give comparable indications of the force required to be exerted with the same strapping in the use of a tool such as isordinarily employed in stretching and crimping or binding the overlapping strapping in a packaging operation. On testing the strapping in the manner described, an indicated slip of from about 5 to about 20 pounds is satisfactory from the standpoint of use of the strapping in securing packages in the conventional manner. The coated materials prepared in accordance with the present invention adequately meet the requirements hereinbefore set forth.

The coating mixtures employed in accordance with the present invention may be prepared by melting the nylon and incorporating the added constituents therein by any suitable method, for example, in a suitable melting pot or in conventional melters of the extruder type; or the materials may be compounded on a compounding mill such as is used for compounding rubber. In use, the coating container or pot is maintained at a temperature of 350 to 560 F., at which temperatures the coating mixture has a sufficiently low viscosity to permit of the formation of very thin coatings, in the order of a thickness of 0.00005 to 0.0006 inch and preferably in the range from 0.00006 to 0.00010 inch. Thicker coatings may be applied, if desired, say to 0.001 inch or thicker.

The thickness of the film is controlled in part by the action of the wipers employed in connection with the coating tank, such as the wipers 23. As hereinbefore indicated, the temperature at which the coating is applied and the speed of travel of the strapping may be varied to control the thickness of the coating. After passing through the coating tank, the coated strapping is cooled or chilled as quickly as possible to solidify the coating, for example, by passing through a quenching water bath, as illustrated at 27, containing water at a temperature below the melting point of the coating composition and suitably at a temperature of 50 to 150 F.

The following examples are illustrative of coatings applied in accordance with the present invention.

Example 1 Blued strapping at an approximate temperature of 700 F. was passed through a bath containing 60% nylon and 40% ester gum derived from high melting point residual rosin (commercially known as Vinsol ester gum) and maintained at a temperature of about 470 F. The coated strapping was then cooled in a water bath as above described. A coating with good adhesion and adequate slip was secured, which gave adequate protection against corrosion. As is readily apparent, pigment or dye may be incorporated in the coating bath, if desired.

Example 2 commercially available under the trade name Hercolyn,

for the methyl ester of abietic acid, similar results are secured.

Example 3 Strapping at a temperature in the order of 650 to 700 F. was passed through a coating bath containing a molten mixture of nylon and technical dehydroabietylamine, (a primary amine derived from rosin and commercially available under the trade name Rosin Amine D) in the proportions of 99 parts of nylon to 1 part of the rosin amine, the mixture being maintained at a temperature of about 462 F. The coated strapping was then cooled in a water bath as above described. The coating mixture was somewhat viscous. The coating secured had adequate adhesion, good slip and was resistant to corrosion.

Similar results were secured with the coating mixture containing 90% nylon and of the rosin amine, the coating bath being maintained at a temperature of about 455 F., the other conditions of operation being similar.

The coated strapping was then cooled as in the preceding examples. In the latter proportions the coating mixture was of low viscosity and flowed or poured freely. The rosin amine as employed in the preceding example appears to have a marked effect in reducing the viscosity of nylon mixtures and has been found particularly suitable for use in small proportions in conjunction with others of the materials admixed with nylon in accordance with the present invention, as hereinbefore set forth.

Example 4 Strapping at a temperature of about 650 to 700 F. was passed into and through a coating bath containing a mixture of nylon and technical n-ethyl-para-toluene-sulfonamide in the proportions of 80% nylon and 20% of the sulfonamide. The coating bath was maintained at a temperature of about 455 F. The coated strapping was then cooled as in the preceding examples. A tough coating was secured with adequate slip properties and which was resistant to corrosion.

Example 5 Strapping, at a temperature in the order of about 700 F., was passed through a coating mixture containing a molten mixture of nylon and myristylamine in the proportions of 90 parts nylon to 10 parts of the amine. The coating bath was maintained at a temperature of about 475 .F. =The coating mixture was of sufficiently low viscosity to pour readily. The coated strapping was then cooled as in the preceding examples. The coating secured had good adhesion and was resistant to corrosion.

Example 6 Strapping at a temperature in the order of 700 F. was passed into and through a coating bath containing a molten mixture of nylon and high melting point residual rosin (commercially available under the name Vinsol), in the proportion of parts nylon to 20 parts of the rosin. The coating mixture was maintained at a temperature of about 490 F. The coated strapping was then cooled as in the preceding examples. An adequate coating was secured which had good adhesion and adequate slip and which was resistant to corrosion.

Example 7 Strapping, at a temperature of 650 to 700 F., was passed through a molten coating mixture containing 60 parts nylon, 20 parts of ester gum derived from high melting residual rosin and 20 parts of technical dehydroabietylarnine. The coating mixture was maintained at a temperature of about 475 F. and apparently by reason of the presence of the rosin amine, was quite fluid. The coated strapping was then cooled as in the preceding examples. A coating having fair adhesion and adequate slip was secured.

Example 8 The strapping at a temperature of about 700 F. was passed through a molten mixture of parts nylon and 10 parts of the acetate of dihydroabietylamine, commercially obtainable as Rosin Amine D Acetate maintained at a temperature of about 475 The coating bath was somewhat more viscous than the coating bath containing the amine, as set forth in Example 3 above. The coated strapping was then cooled as in the preceding examples. An excellent coating was obtained having good adhesion, adequate slip and resistant to corrosion.

Example 9 Asia the preceding examples, the strapping at a temperature in the order of 700 F. was passed through a molten mixture containing 60 parts nylon, 30 parts of the glycerol ester of hydrogenated rosin known commercially as Staybelite Resin No. 10, 30 parts of n-ethyl-paratoluene sulfonamide and 30 parts of residual high melting rosin or Vinsol. The coating mixture was maintained at 420 F. and at this temperature was slightly viscous. The coated strapping was then cooled as in the preceding examples. A coating of adequate slip was obtained, which had good adhesion and was resistant to corrosion.

The nylon employed in the foregoing examples was a polymer of the amide derived from hexamethylene diamine and adipic acid and is commercially available under the grade mark FM-6501. The melting point (in nitrogen) of the polymer mixture obtainable under this grade mark varies from to 215 C. The material used in the foregoing examples had a melting point of about 215 C. Materials of the same grade mark with lower melting points give similar results and are somewhat more readily compounded.

In other tests, use was made of a nylon having a listed melting point of 455 F. or about 235 C., but having melting points fordifierent samples ranging from 173 C. to 209 C., was employed. In this series of examples, the

effect of different thicknesses of coating on slip were determined. The nylon used in these experiments is commercially designated by the grade mark FM-3001 and on examination appears to be a mixture of polymers of the amide, resulting from the reaction of hexamethylene diamine and adipic acid.

Example 10 The strapping was prepared as in commercial operation by being passed through a lead bath at about 850 F., emerging through a charcoal chute as hereinbefore indicated. The temperature of the strap as it entered the coating bath was in the order of 650 F. The coating bath consisted of a mixture of 80 parts nylon and 20 parts of residual high melting point rosin (Vinsol) and was maintained at a temperature of 450 F. The strapping was 4 inch wide and 0.020 inch thick and was passed through the system at a rate of 25 feet per minute. The wipers were set so that the thickness of the coating was 0.00006 inch. The strapping after coating, was promptly passed through a water bath at a temperature of 160 F. The coated strap was tested for slip in equipment giving results comparable to those secured by the method previously described. As tested in this equipment, the slippage was 15 pounds. In another test under similar conditions, in which the coating equipment was adjusted to give a coating having a thickness of 0.00018 inch, the slippage test showed a slip of 10 pounds.

Additional operations with mixtures of the nylon and of the residual, high melting point rosin (Vinsol) containing 10% and 33% Vinsol likewise gave satisfactory coatings.

Example 11 This operation was conducted in a manner similar to the preceding Example 10, the coating mixture in this example consisting of 95% nylon and of dihydroabietylamine. The speed of travel of the strapping through the equipment was 300 to 325 feet per minute. The temperature of the coating bath was approximately 500 (F. and the temperature of the cooling water bath was 110 F. In different operations the thickness of the coatings were controlled to 0.00007 inch, 0.00009 inch and 0.00019 inch. Excellent adherent flexible coatings were obtained and the slippage, as determined for each of these coatings, was in the narrow range of from to 13 pounds.

Example 12 In this example the method of operation was as described in the two preceding examples, the temperature of the lead bath being slightly higher, about 860 F. The coating bath consisted of 73% nylon, 25% high melting point residual rosin (Vinsol) and 2% dihydroabietylamine (Rosin Amine D). The speed of travel of the strapping was 480 feet per minute. The coating bath temperature was about 500 F. and that of the cooling water bath was about 130 F. With a thickness of coating of 0.00009 inch, an excellent adherent coating was obtained which, on testing as hereinbefore described, had a slip of about 11 pounds.

In similar operations with the same coating, and under the same conditions except that the speed of movement of the strapping was 300 feet per minute and the temperatureof the molten bath of coating mixture was in the order of 540 F., coatings were produced having thicknesses ranging from 0.0005 inch to 0.00009 inch. Good coatings were obtained and the slip of these coatings, when tested as above described, ranged from 7 pounds to 11 pounds.

In the foregoing examples the speed of travel of the strapping varied from 250 to 480 feet per minute. Higher speeds may be employed, say to 750 feet per minute, or higher.

In the foregoing examples, where it is indicated that a good coatingwas-secured, it-is to be understood that this signifies that the coating was adherent, hard, had suffi} cient flexibility to be employed in the usual equipment for strapping packages without cracking or breaking and had adequate corrosion resistance.

With regard to the temperatures of the strapping before entering the melting bath, as given in the foregoing Examples 10; 11 and 12, it is to be understood that the meansavail'able permitted only a rough approximation of the actual temperatures of the strapping. The temperatures given are therefore subject to a possible error of say plus or minus 50, but in all cases are higher than the temperature of the coating mixture, in general by at least 50. In referring to these temperatures the expression in the order of has been employed in the examples to indicate that the temperature given is a rough approximation.

A disclosure of a. composition suitable for use in carrying out the foregoing invention is contained in the application of one of us (John J. Hickerson), Serial No. 355,165, filed May 14, 1953.

The coated strapping prepared in accordance with the present invention may be employed satisfactorily in packaging operations instead of the waxed steel strappingor the enameled and waxed steel strapping which has hitherto been employed. Without a superficial wax coating, it may be employed satisfactorily in the customary equipment used for applying, tightening and binding. strapping on boxes, bales and other packages. As is readily apparent, the process may also be applied to other metallic ligature materials, for example, to iron or steel wire such as is used in similar packaging operation.

Vie claim:

1. The method of preparing a coated metallic ligature material having abrasion and corrosion resistance which comprises melting a mixture containing a major proportion ofa nylon resin together with a softening agent of the group consisting of abietic acid derivatives, long chain aliphatic amines having 12 to 16 carbon atoms and alkyl aryl sulfonamides, applying the molten mixture. to the surface of such ligature material while the ligature is at a temperature at least as high as that of the melted mixture and cooling the coated ligature material.

2. The method of claim 1 wherein the ligature material is at a temperature in the order of 50 to 200 F. above the temperature of the coating mixture prior to entering the coating mixture.

3. The method of preparing a coated metallic ligature material having abrasion and corrosion resistance, which comprises melting a mixture containing a major proportion of nylon resin together with an abietic acid derivative of the class consisting of resin and residual high melting point rosin, the methyl esters of abietic acid and dihydro abietic acid, the glycerol esters of rosin and of hydrogenated rosin, dehydroabietyl amine and its salts with lower fatty acids, applying the molten mixture to the surface of such ligature material while the ligature is at a temperature at least as high as that of the melted mixture and cooling the coated ligature material.

4. The method of claim 3 wherein the ligature material is at a temperature in the order of 50 to 200 F. above the temperature of the coating mixture prior to entering the coating mixture.

5. The method of preparing a coated steel strapping having abrasion and corrosion resistance and surface friction characteristics permitting slippage of contacting surfaces of the strapping over each other under pressure in tightening and bonding the strapping material when used in packaging, which comprises applying to the surfaces of such strapping a thin coating of a molten mixture containing a major proportion of a nylon together with an abietic acid derivative of the class consisting of rosin and residual high melting point rosin the methyl esters of abietic acid and dihydroabietic acid, the glycerol esters of rosin and hydrogenated rosin, dihydroabietylamine and its saltswith lower fatty acids, said strappingat-the time of application of the molten mixture being at a temperature in the order of 50 to 200 F. above the temperature of the coating mixture.

6. The method of preparing a coated metallic ligature material having abrasion and corrosion resistance, which comprises applying to the surfaces of such ligature material a thin coating of a molten mixture containing a major proportion of a nylon, together with an alkyl aryl sulfonarnide, the ligature material being heated prior to coating to a temperature at least as high as that of the molten coating mixture, and cooling the coated ligature material.

7. The method of claim 6, wherein the alkyl aryl sulfonamide is n-ethyl-para-toluene sulfonamide.

8. The method of preparing a coated steel strapping having abrasion and corrosion resistance which comprises melting a mixture containing a major proportion of a. nylon resin together with a softening agent of the group consisting of abietic acid derivatives, long chain aliphatic amines having 12 to 16 carbon atoms and alkyl aryl sulfonamides, applying the molten mixture to the surface of such steel strapping while the strapping is at a temperature at least as high as that of the melted mixture and cooling the coated steel strapping.

9. The method of claim 8 wherein the strapping is at a temperature in the order of 50 to 200 F. above the temperature of the coating mixture prior to entering the coating mixture.

10. The method of preparing a coated steel strapping having abrasion and corrosion resistance, which comprises applying to the surfaces of the strapping a coating of a molten mixture containing a major proportion of a nylon together with a long chain aliphatic amine having 12 to 16 carbon atoms, the strapping being heated prior to coating to a temperature at least as high as that of the molten coating mixture, and cooling the coated strapping.

11. The method of claim 10 wherein the amine is myristyl amine and the ratio of nylon to amine in the coating mixture is 9 to 1.

12. The method of preparing a coated steel strapping having abrasion and corrosion resistance, which comprises applying to the surfaces of the strapping a coating of a molten mixture containing a major proportion of a nylon together with an alkyl aryl sulfonamide, the strapping being heated prior to coating to a temperature at least as high as that of the molten coating mixture, and cooling the coated strapping.

13. The method of claim 12 wherein the alkyl aryl sulfonamide is n-ethyl-para-toluene sulfonamide.

14. The method of preparing a coated steel strapping having abrasion and corrosion resistance, which comprises heating the strapping, passing the strapping continuously through a molten mixture of a nylon with 1 to 50% of a softening agent of the class consisting of the abietic acid derivatives, long chain aliphatic amines having 12 to 16 carbon atoms and alkyl aryl sulfonamides, the temperature of the coating mixture being in the range from 350 to 550 F. and the temperature of the strapping before entering the coating bath being at least as high as that of the coating bath, reducing the thickness of the coating on the strapping to 0.00005 to 0.0006 inch and cooling the coated strapping.

15. The method of claim 14 wherein the proportion of the softening material in the coating bath is 10 to 33%.

16. The method of preparing a coated steel strapping having abrasion and corrosion resistance and surface friction characteristics permitting slippage of the contacting surfaces of the strapping over each other under pressure in tightening and bonding the strapping when used in packaging, which comprises heating the strapping, passing the strapping continuously through a molten mixture of a nylon with 1 to 50% of an abietic acid derivative of the class consisting of rosin and residual high melting point rosin, the methyl esters of abietic acid and dihydroabietic acid, the glycerol esters of rosin and by drogenated rosin, dihydroabietylamine and its salts with lower fatty acids, the temperature of the coating mixture being in the range from 350 to 550 F. and the temperature of the strapping before entering the coating bath being at least as high as that of the coating bath, controlling the thickness of the coating on the strapping and cooling the coated strapping.

17. The method of claim 16 wherein. the proportion of the softening material in the coating bath is 10 to 33 18. The method of preparing a coated steel strapping having abrasion and corrosion resistance and surface friction characteristics permitting slippage of contacting surfaces of the strapping over each other under pressure in tightening and bonding the strapping when used in packaging, which comprises continually passing the strapping through a lead bath maintained at a temperature of 750 to 950 F. and through a chamber having a reducing atmosphere on emerging from said lead bath, and passing the strapping while hot through a molten mixture of nylon and residual high melting point rosin, the proportion of rosin therein being 10 to 33% and said bath having a temperature of 350 to 560 F., the temperature of the strapping on entering said bath being at least as high as the temperature of the bath, controlling the thickness of the coating on the strapping on emerging from said bath, and immersing said strapping in water, thereby cooling the coated strapping.

19. The method in accordance with claim 18 wherein the proportion of the high melting point rosin in the coating mixture is 20% 20. The method of claim 18 wherein. the temperature of the strapping on entering the coating mixture is about 50 to 200 F. above that of the coating mixture. '21. The method of preparing a coated steel strapping having abrasion and corrosion resistance and surface friction characteristics permitting slippage of contacting surfaces of the strapping over each other under pressure in tightening and bonding the strapping when used in packaging, which comprises continually passing the strapping through a lead bath maintained at a temperature of 750 to 950 F. and passing the strapping while hot through a molten mixture of nylon and methyl abietate in the ratio of nylon and 10% of methyl abietate, said bath having a temperature of 350 to 560 F. and the temperature of the strapping on entering said bath being at least as high as the temperature of the bath, controlling the thickness of the coating on the strapping on emerging from said bath, and immersing said strapping in water, thereby cooling the coated strapping.

22. The method of preparing a coated steel strapping having abrasion and corrosion resistance and surface friction characteristics permitting slippage of contacting surfaces of the strapping over each other under pressure in tightening and bonding the strapping when used in packaging, which comprises continually passing the strapping through a lead bath maintained at a temperature of 750 to 950 F. and passing the strapping while hot through a molten mixture of nylon and dihydroabietylamine in the ratio of nylon and 5% of dihydroabietylamine, said bath having a temperature of 350 to 560 F. and the temperature of the strapping on entering said bath being at least as high as the temperature of the bath, controlling the thickness of the coating on the strapping on emerging from said bath, and immersing said strapping in water, thereby cooling the coated strapping.

23. The method of preparing a coated steel strapping having abrasion and corrosion resistance, which comprises continually passing the strapping through a lead bath maintained at a temperature of 750 to 950 F. and passing the strapping while hot through a molten mixture of nylon and n-ethyl-para-toluene sulfonamide in the ratio of 80% nylon and 20% of the sulfonarnide, said bath having a. temperature of 350 to 560 Fraud the temperature of the strapping on entering said bath be 1 1 ing at least as high as the temperature of the bath, controlling the thickness of the coating on the strapping onemerging from said bath, and immersing said strapping in Water, thereby cooling the coated strapping.

24. The method of preparing a coated steel strapping having abrasion and corrosion resistance, which comprises continually passing the strapping through a lead bath maintained at a temperature of 750 to 950 F. and passing the strapping while hot through a molten mixture of nylon and dihydroabietylamine acetate in the ratio of 90% nylon and of the amine acetate, said bath having a temperature of 350 to 560 F. and the temperature of the strapping on entering said bath being at least as high as the temperature of the bath, controlling the thickness of the coating on the strapping on emerging from said bath, and immersing said strapping in water, thereby cooling the coated strapping.

25. The method of preparing a coated steel strapping having abrasion and corrosion resistance, which comprises continually passing the strapping through a lead bath maintained at a temperature of 750 to 950 F. and passing the strapping while hot through a molten mixture of 90 parts nylon and 10 parts of myristylamine, said bath having a temperature of 350 to 560 F. and the temperature of the strapping on entering said bath being at least as high as the temperature of the bath, controlling the thickness of the coating on the strapping on emerging from said bath and immersing said strapping in water, thereby cooling the coated strapping.

26. The method of preparing a coated steel strapping having abrasion and corrosion resistance and surface friction characteristics permitting slippage of contacting surfaces of the strapping over each other under pressure in tightening and bonding the strapping when used in packaging, which comprises continually passing the strapping through a lead bath maintained at a temperature of 750 to 950 F. and passing the strapping while hot through a molten mixture of 73% nylon, 25% residual high melting point rosin and 2% dehydroabietylamine, said bath having a temperature of about 500 F. and the temperature of the strapping on entering said bath being at least as high as the temperature of the bath, controlling the thickness of the coating on the strapping on emerging from said bath, and immersing said strapping in water, thereby cooling the coated strapping.

27. The method of preparing a coated steel strapping having abrasion and corrosion resistance and surface friction characteristics permitting slippage of contacting surfaces of the strapping over each other under pressure in tightening and bonding the strapping when used in packaging, which comprises continually passing the strapping through a lead bath maintained at a temperature of 750 to 950 F. and passing the strapping while hot through a molten mixture of 60 parts nylon, 30 parts of the glycerol ester of hydrogenated rosin and 30 parts residual high melting point rosin, said bath having a temperature of 350 to 560 F. and the temperature of the strapping on entering said bath being at least as high as the temperature of the bath, controlling the thickness of the coating on the strapping on emerging from said bath, and immersing said strapping in water, thereby cooling the coated strapping.

28. Steel strapping for securing and binding packages and the like, said strapping having a fused coating of a plastic material containing about 66 to 90% nylon and 10 to 33% of residual high melting point rosin, said coating being of a thickness of 0.00005 to 0.001 inch and being flexible, corrosion resistant and tenaciously adhered to the'base metal so as to withstand bending.

29. Steel strapping for securing and binding packages and the like, said strapping having a fused coating of a plastic material containing about 66 to 90% nylon and 10 to 33% of residual high melting point rosin, said coat ingbeing of a thickness of0.00005' to 0.0006 inch and being flexible; corrosion resistantand tenaciouslyadhered 12 to the base metal so as to withstand bending and having a slip of 5 to 20 pounds, when determined substantially as described.

30. The article of manufacture of claim 29 wherein the fused coating is of a plastic material containing about nylon and 20% of the rosin.

31. Steel strapping for securing and binding packages and the like, said strapping having a fused coating of a plastic material containing about nylon and 10% of methyl abietate, said coating being of a thickness of 0.00005 to 0.001 inch and being flexible, corrosion resistant and tenaciously adhered to the base metal so as to withstand bending.

32. Steel strapping for securing and binding packages and the like, said strapping having a fused coating of a plastic material containing about nylon and about 5% of dihydroabietylamine, said coating being of a thickness of 0.00005 to 0.001 inch and being flexible, corrosion resistant and tenaciously adhered to the base metal so as to withstand bending.

33. Steel strapping for securing and binding packages and the like, said strapping having a fused coating of a plastic material containing about 80% nylon and about 20% of n-ethyl-para-toluene sulfonamide, said coating being of a thickness of 0.00005 to 0.001 inch and being flexible, corrosion resistant and tenaciously adhered to the base metal so as to withstand bending.

34. Steel strapping for securing and binding packages and the like, said strapping-having a fused coating of a plastic material containing about 90% nylon and about 10% of dihydroabietylamine acetate, said coating being of a thickness of 0.00005 to 0.001 inch and being flexible, corrosion resistant and tenaciously adhered to the base metal so as to withstand bending.

35. Steel strapping for securing and binding packages and the like, said strapping having a fused coating of a plastic material containing 90% nylon and about 10% myristylamine, said coating being of a thickness of 0.00005 to 0.001 inch and being flexible, corrosion resistant and tenaciously adhered to the base metal so as to withstand bending and having a slip of 5 to 20 pounds, when determined suubstantially as described.

36. Steel strapping for securing and binding packages and the like, said strapping having a fused coating of a plastic material containing about 73% nylon, about 25 of residual high melting point rosin and, about 2% of dihydroabietylamine, said coating being of a thickness of 0.00005 to 0.001 inch and being flexible, corrosion resistant and tenaciously adhered to the base metal so as to withstand bending.

37. Steel strapping for securing and binding packages and the like, said strapping having a fused coating of a plastic material containing about 73% nylon, about 25% of residual high melting point rosin, and about 2% of dihydroabietylamine, said coating being of a thickness of 0.00005 to 0.0006 inch and being flexible, corrosion resistant and tenaciously adhered to the base metal so as to withstand bending and having a slip of 5 to 20 pounds, when determined substantially as described.

38. Steel strapping for securing and binding packages and the like, said strapping having a fused coating of a plastic material containing about 60 parts nylon, about 30% of the glycerol ester of hydrogenated resin and about 30% of residual high melting point rosin, said coating being of a thickness of 0.00005 to 0.0006 inch and being flexible, corrosion resistant and tenaciously adhered to the base metal so as to withstand bending and having a slip of 5 to 20 pounds, when determined substantially as described.

39. Ligature material containing iron as a predominant constituent having a thin fused adherent coating of a plastic material containing nylon resin as its major constituent and a softening agent selected from the group consisting of abietic acid derivatives, long chain aliphatic amines'having l2-to 16 carbon atoms and-alkyl aryl sulfonamides, said coating being of a thickness of 0.00005 to 0.001 inch.

References Cited in the file of this patent Balthis et a1. Jan. 19, 1943 14 Roskosky Aug. 31, 1943 Brubaker Sept. 28, 1943 Buechele Feb. 22, 1949 Hall Mar. 3, 1953 Foster Dec. 1, 1953 C-hadbom'ne Feb. 23, 1954 Amundsen et a1. Nov. 30, 1954 

1. THE METHOD OF PREPARING A COATED METALLIC LIGATURE MATERIAL HAVING ABRASION AND CORROSION RESISTANCE WHICH COMPRISES MELTING A MIXTURE CONTAINING A MAJOR PROPORTION OF A NYLON RESIN TOGETHER WITH A SOFTENING AGENT OF THE GROUP CONSISTING OF ABIETIC ACID DERIVATIVES, LONG CHAIN ALIPHATIC AMINES HAVING 12 TO 16 CARBON ATOMS AND ALKYL ARYL SULFONAMIDES, APPLYING THE MOLTEN MIXTURE TO THE SURFACE OF SUCH LIGATURE MATERIAL WHILE THE LIGATURE IS AT A TEMPERATURE AT LEAST AS HIGH AS THAT OF THE MELTED MIXTURE AND COOLING THE COATED LIGATURE MATERIAL. 